back to article Earth's night-side gets different kinds of neutrinos from day-side

A Japanese neutrino detector has provided experimental evidence for a prediction first made in the 1980s: that passing through something good and massive – like the Earth – will influence the flavour of neutrinos. Analysing 18-years' worth of data collected by subterannean neutrino detector SuperKamiokande has shown that the …


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  1. John Robson Silver badge

    how many

    interactions have they seen/year - against how many neutrinos?


    1. Michael H.F. Wilkinson Silver badge
      Thumb Up

      Re: how many

      One of the better whatif.xkcd pages. Thanks for that

  2. Tom 7

    Hang on there

    "For neutrinos of higher energies, however, a larger fraction change, meaning that fewer electron neutrinos are detected.”

    Shirley higher energy neutrinos would be travelling nearer the speed of light so time would travel more slowly for them so the opposite should be true? Or are they just not changing for an nth time?

    1. Ken Hagan Gold badge

      Re: Hang on there

      All neutrinos are travelling at some ridiculous number of nines of the speed of light. I don't know if I ever knew why interactions are more likely with higher energy neutrinos, but I've certainly forgotten if I ever did. It's probably complicated. Perhaps someone will jump in here...

      1. Scroticus Canis

        Re: Hang on there

        Basically as you move from left to right on a standard model diagram the particles mass/energy increases which is why you normally only see Up and Down quarks in matter in the 'normal environment'.

        The heavier quarks and neutrinos are only found where there is high environmental energy; stellar cores, thermo-nuke blasts, accelerators, etc.. and rapidly decay to lower energy form particles once out of that environment.

        Quantum mechanics allows morphing in either direction so give a light electron-neutrino enough energy and it can morph into a heavier muon-neutrino flavour, more still and it can morph into the heavier still tau-neutrino. As the heavier neutrinos lose energy (moving through the earth in this case) they morph back to lower mass/energy forms. The energy/mass changes accommodate the extra energy as the C limit cant be exceeded.

        That's the very simplified explanation which my mind likes and is basically how it works; the full catastrophe quantum mechanical maths just makes my head hurt.

        Beer icon because I now need one - heading to the fridge.

        1. Chris T Almighty

          Re: Hang on there

          Never trust a man who starts a sentence about neutrinos with the word 'basically'.

        2. annodomini2

          Re: Hang on there

          @Scroticus Canis,

          Did the Beer turn into Cider through energy loss?

    2. Anonymous Coward
      Anonymous Coward

      Re: Hang on there

      Higher energy is not always correlated with higher speed IIRC. As in, a photo always* travels at light speed but can have varied energies. Hence a neutrinos energy and speed are not correlated I would assume.

      *check wiki etc for a breakdown of how observed speed can differ, but the "lightspeed" remains the same.

      1. Martin Budden Silver badge

        Re: Hang on there

        a photo always travels at light speed

        As demonstrated by the Streisand effect.

      2. Anonymous Coward
        Anonymous Coward

        Re: Hang on there

        Hmm, a thumb down and no explanation. If I've gone wrong somewhere at least point it out. Ah, I typed "photo" instead of "photon"? Wow, tough crowd. :P

    3. Alan Brown Silver badge

      Re: Hang on there

      It's because time travels more slowly for faster-moving neutrinos that we can see them more easily. The glow is smeared out over a longer trail.

      The same applies for cosmic ray interactions. Readily observable relativistic effects. :)

  3. Vince Lewis 1

    Hollywood has got it right

    Mutant neutrinos are going to boil the earth and bring about the end of the world.

    John cussak is holding my coat.

    1. Vladimir Plouzhnikov

      Re: Hollywood has got it right

      Yes, and the detector is called Super-Kamikaze or something... The end is nigh, the tickets are expensive and the world is in a pissing match with the Russians - so not a chance of getting a lift in one of those An-124s. Oh, well...

  4. Anonymaus Cowark
    IT Angle

    and the IT angle is



    1. JDX Gold badge

      IT is used to process the data?

  5. Rustident Spaceniak

    Let's see- Smirnoff, Wolfenstein?

    So Mikhey had a few Smirnoffs and after playing Wolfenstein for years, came up with this great theory about Neutrinos? I could have done as much in a day! With all the discarded coffee pads around on dumps, it's clear anything passing through Earth will change flavour.

    OK now: The super kamio thing is, as far as one recalls, just one of several neutrino detectors out there. Surely the others, which all suffer the same fate of being alternatively in day- and nighttime, will be able to offer corroborating data?

    On second thoughts, there's a faint memory someone wanted to build a detector in the Antarctic. Obviously, with there being less of Earth down there to pass through, the change of flavour should be correspondingly less pronounced?

    1. MacGyver

      Re: Let's see- Smirnoff, Wolfenstein?

      I agree, why couldn't the lower energy neutrinos have come from space? I think what you said in your last sentence would go along way to eliminating the possibility that they are just space-borne lower energy odd neutrinos. Hell, why can't we make a small-scale neutrino detector, make it space-borne, and send it out Voyager style.

      Afterthought, couldn't you build a neutrino "shield" below a neutrino detector by generating huge amounts of neutrinos from side by side mounted high energy lasers. Basically increasing the likelihood that any neutrino that may have passed through the other side of the Earth would collide with the perpendicular "wall" of neutrinos under the detector, and then better proving that it didn't simply originate from space? If that would indeed work, couldn't you build "shields" completely around a detector and shoot neutrinos from a moving source on the opposite side of the Earth through the Earth directly at the detector, and allow only neutrinos from that direction into the detector, kind of like a neutrino x-ray machine for mapping the different densities inside of the Earth.

      I may have watched too much SyFy channel and a little too much to drink last night.

  6. Anonymous Blowhard

    Is SuperKamio Wii only or also on DS?

    Are any politicians aware of the threat from neutinos coming from above (or below depending on time of day)?

    Enquiring minds are bored with work already...

  7. Andy The Hat Silver badge

    The neutrino flux changes day/night. Good science, nice result.

    Correct conclusion: lower electron neutrino flux at night ...

    Reported conclusion: The electron neutrinos change flavour so the flux reduces and we don't detect so many. Theory, no practical experimental evidence, terrible science!

    The excess neutrinos, using the same experimental evidence but according to my theory, are absorbed by the fillings of Mr Kipling jam tarts in London, there's just as much evidence! Lots of other less jammy possibilities, including absorption by some mechanism within the Earth but, until they do an experiment showing the increase in flux of the other neutrinos with the corresponding drop in flux of electron neutrinos, their conclusion is not shown by the experimental evidence.

    A Level physics score 5 out of 10, results good but mis-interpretation of results resulting in an invalid conclusion based on the available data.

    1. Anonymous Coward

      I do agree some do bad science sometimes, but...

      I do agree some people do bad science sometimes, but not in this instance...

      The prediction of change is possibly related to the mass/gravity of earth. Thus we have a specific value to test against.

      If your theory is correct, and I eat all the Kiplings Jam Tarts, then we will see a change. :)

      If the scientific theory is correct, we can possibly measure a change relative to earth, moon and other large bodies (planets or myself after eating all the Jam Tarts).

      Thus, while still a theory, and as mentioned in the article, not a "discovery", it is at least honest in it's approach to science. We would find further information through more study, data and confirmation. Take in point how most of these experiments also require secondary or tertiary confirmation using separate methods (see LHC for an example where 1 multi billion dollar experiment is still not considered "evidence" in it's own isolation).

      Thus, as each experiment uses separate methods, systematic errors are unlikely to move between each. Using 3 points of data then gives the ability to see if 1 or more is erroneous (like an airplanes triple calculation computers for error detection).

      Basically, if this was a distance measure, they would use a tape measure, a lasar range finder and sonar to triple check a distance to make sure no scientist, instrument or theory was in error.

    2. Julian Bradfield

      Andy the Hat: Those who mark A-level Physics can generally read the sign of the reported result correctly.

    3. Old Handle

      The article clearly states they saw more neutrinos at night, not less. This does not suppose your conclusion.

      Eyewear for jam splatter protection. -->

    4. PassingStrange

      Your tarts are post hoc. This isn't,

      The theory predicted this; the experiment bears out the prediction. Good science.

  8. JDX Gold badge

    I would like to go in that tank

    The ultimate in sensory deprivation.

    50000 tons of water, that's basically a 120 foot cube?

  9. John Smith 19 Gold badge

    One moment.

    This detector cannot detect the Tau and Muon neutrinos, it only detects the electron kind.

    So to actually reach the conclusion proposed you'd need to measure the Tau and Muon types as well.

    Otherwise the chain of logic is not complete.

    1. Rustident Spaceniak

      Re: One moment.

      That's perfectly correct. Nonetheless, at least for muon neutrinos, the detection rate should be measureable with the OPERA and Icecube detectors. Not sure if those have detected enough neutrinos yet to evaluate a decent daily rate.

      Concerning electron neutrinos, as I hinted at above, the results from Supermario should now be correlated with those of other detectors looking specifically at solar neutrinos, then we'll be able to judge whether it's the Earth or Jam Tarts that cause the more energetic ones to deteriorate into electron neutrinos. Failing that, a different theory would have to be established that accounts for a 24h variation cycle in the number of neutrinos detected.

    2. BristolBachelor Gold badge

      Re: One moment.

      You have a point, and I'm waiting to read your paper on the subject. I enjoy reading your posts, so I await with baited breath :)

      The paper should at least hypothesise the mechanism that affects the sun depending on which side of the Earth is facing it. Ideally, it should also say how this mechanism changes the rate at which it fires neutrinos at us that are detected as electron neutrios.

  10. John G Imrie

    This sounds like the

    'Hum that's weird' moment where science starts.

  11. Andy The Hat Silver badge

    I've started eating jam tarts ... anyone noticed a flux change yet? :-)

  12. Mike Moyle

    Depending on how many data points they have...

    Shouldn't there be at least SOMETHING resembling a bell-curve measuring from noon to noon with highest numbers of electron neutrinos at midnight? As more of the earth intervenes between detector and sun, the number of neutrinos decaying to the electron flavored-ones should increase, if only slightly, right?

    1. Sporkinum

      Re: Depending on how many data points they have...

      I think that's the point. Not enough data points for enough confidence. Since Super-Kario only detects electron neutrinos, the speculation is that interaction with the earth is transmogrifying a few the other types as they go through. With enough data, I would guess there would be a bell curve. I guess that's why they want to make a Hyper-Kario.

  13. ammabamma

    I would've gotten away with it if it hadn't been for those meddling kids


    I think "they" are starting to cotton on to my extra-legal, "off the books" neutrino dumping program.

    (Carbon credits? pfffft. Neutrino credits are where its at now!)

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